Symptoms such as a diarrhea, a constipation, and an abdominal pain are observed in diseases with various organic changes of the gastrointestinal tract (e.g., an infection of the gastrointestinal tract and a tumor). On the other hand, such symptoms are also observed in many diseases in which no organic abnormality is recognized by an endoscopic examination or an examination using a contrast medium. Regarding diseases expressing these symptoms, global diagnostic criteria have been determined, and Rome III criteria have been published in 2006 as the current diagnostic criteria, which categorize diseases particularly based on the domain where a symptom is expressed. Patients have been classified into various diseases in accordance with these diagnostic criteria and received necessary medical treatments.
Moreover, many alimentary symptoms which are not categorized by the above diagnostic criteria are also observed. In actual clinical trials, the quality of life (QOL) of patients has been also evaluated. For example, in a clinical trial of a functional dyspepsia, Gastrointestinal Symptom Rating Scale (GSRS) has been widely used for estimating the QOL. The evaluation item includes (1) acid reflex, (2) abdominal pain, (3) indigestion, (4) diarrhea, (5) constipation and others, and has been graded and evaluated.
Heretofore, it has been difficult to identify a cause of development (or sideration) or to select a diagnostic or treatment technique for a functional gastrointestinal disorder in which no organic or pathologic change has been recognized. As a result, there has been some confusion, distrust, and misunderstanding among physicians, patients, and the general public. In addition, as described in Gastroenterol 130, 1377-1390, 2006 (Non-Patent Document 1), the tendency has been to overemphasize stress as the cause of development. At present, there is insufficient treatment technique for diseases categorized based on the diagnosis by the Rome III criteria or the like, except part of diseases. As the result of the disclosure of the diagnostic criteria, it has been further expected to clarify the cause of development of each disease or to study the corresponding precise treatment technique in the future. Thus, a control substance of a neurotransmitter (serotonin) involving or engaging to the motility of the intestinal tract was developed for a specific functional gastrointestinal disorder. However, after placing on the market, the control substance canceled a sale due to side effects thereof. Thus therapeutic drugs having no side effect have been strongly required.
On the other hand, Japanese Patent No. 61-23192 (JP-61-23192B, Patent Document 1) mentions that a compound “rifaximin” synthesized as a rifamycin derivative is an antibiotic having an activity to various species of a Gram-positive strain, a Gram-negative strain, an aerobic bacteria, and an anaerobic bacteria. Moreover, since rifaximin is not absorbed systemically, a first significant characteristic of rifaximin is to express no side effect when administered to the human body. Further, due to no systemic absorption, a second significant characteristic is to have neither adverse influence, in blood, to kinetics of other drugs which are used in combination with rifaximin nor drug interactions.
Rifaximin has been already widely used as a therapeutic agent for intestinal infection, hepatic encephalopathy, and skin infection. In addition, regarding rifaximin, the followings are mentioned: rifaximin has been marketed in the United States as a drug adaptable for the treatment of traveler's diarrhea (12 years of age or older) caused by noninvasive Escherichia coli [Annals of Internal Medicine, 142(10), p. 805-812, 2005 (Non-Patent Document 2)]; rifaximin is useful for preventing or treating bacterial colpopathy [Japanese Patent No. 2834951 (JP-2834951B, Patent Document 2)]; rifaximin is useful for preventing or treating gastric indigestion caused by Helicobacter pylori [Japanese Patent No. 2755550 (JP-2755550B, Patent Document 3)]; rifaximin is useful for preventing or treating diarrhea caused by cryptosporidiosis [Japanese Patent Application Laid-Open No. 226645/1998 (JP-10-226645A, Patent Document 4)]; rifaximin is useful for preventing or treating irritable bowel syndrome (IBS) or the like (International Publication WO 01/11077 pamphlet (Patent Document 5) and Annals of Internal Medicine, 145(8), p. 557-563, 2006 (Non-Patent Document 3)).
However, findings of rifaximin on a functional gastrointestinal disorder (particularly, a functional gastroduodenal disorder) have not been obtained. Moreover, an agent for preventing or treating a functional gastrointestinal disorder (particularly, a functional gastroduodenal disorder) containing rifaximin as an effective ingredient has not been known.